There is a plethora of references (both patents and literature articles) dealing with the formation of intermediate oxidation products, such as for example acids, one of the most important being adipic acid, by oxidation of hydrocarbons. Adipic acid is used to produce Nylon 66 fibers and resins, polyesters, polyurethanes, and miscellaneous other compounds.
There are different processes of manufacturing adipic acid. The conventional process involves a first step of oxidizing cyclohexane with oxygen to a mixture of cyclohexanone and cyclohexanol (KA mixture), and then oxidation of the KA mixture with nitric acid to adipic acid. Other processes include, among others, the "Hydroperoxide Process," the "Boric Acid Process," and the "Direct Synthesis Process," which involves direct oxidation of cyclohexane to adipic acid with oxygen in the presence of solvents, catalysts, and initiators or promoters.
The Direct Synthesis Process has been given attention for a long time. However, to this date it has found little commercial success. One of the reasons is that although it looks very simple at first glance, it is extremely complex in reality. Due to this complexity, one can find strikingly conflicting results, comments, and views in different references. It is also important to note that most studies on the Direct Oxidation have been conducted in a batch mode, literally or for all practical purposes.
There is a plethora of references dealing with oxidation of organic compounds to produce acids, such as, for example, adipic acid and/or other intermediate oxidation products, such as for example cyclohexanone, cyclohexanol, cyclohexylhydroperoxide, etc.
The following references, among the plethora of others, may be considered as representative of oxidation processes relative to the preparation of diacids and other intermediate oxidation products.
U.S. Pat. No. 5,463,119 (Kollar), U.S. Pat. No. 5,374,767 (Drinkard et al.), U.S. Pat. No. 5,321,157 (Kollar), U.S. Pat. No. 3,987,100 (Barnette et al.), U.S. Pat. No. 3,957,876 (Rapoport et al.), U.S. Pat. No. 3,932,513 (Russell), U.S. Pat. No. 3,530,185 (Pugi), U.S. Pat. No. 3,515,751 (Oberster et al.), U.S. Pat. No. 3,361,806 (Lidov et al.), U.S. Pat. No. 3,234,271 (Barker et al.), U.S. Pat. No. 3,231,608 (Kollar), U.S. Pat. No. 3,161,603 (Leyshon et al.), U.S. Pat. No. 2,565,087 (Porter et al.), U.S. Pat. No. 2,557,282 (Hamblet et al.), U.S. Pat. No. 2,439,513 (Hamblet et al.), U.S. Pat. No. 2,223,494 (Loder et al.), U.S. Pat. No. 2,223,493 (Loder et al.), German Patent DE 44 26 132 A1 (Kysela et al.), and PCT International Publication WO 96/03365 (Constantini et al.).
None of the above references, or any other references known to the inventors disclose, suggest or imply, singly or in combination, oxidation reactions to intermediate oxidation products under conditions subject to the intricate and critical controls and requirements of the instant invention as described and claimed.
Our U.S. Pat. Nos. 5,580,531, 5,558,842, 5,502,245, as well as our PCT International Publication WO 96/40610 describe methods and devices relative to controlling reactions in atomized liquids.